A process for making 2,3,5-trichloropyridine and 2,4,4-trichloro-4-formylbutyronitrile from trichloroacetaldehyde and acrylonitrile is described in European patent application No. 12117.
The preparation of 2,2-dichloroaldehydes is described by DeBuyck et al, Bull. Soc. Chem. Belg. 89, 441 (1980) and in copending application Ser. No. 487,476, filed Apr. 22, 1983.
European patent application No. 46735 describes and claims a process for the preparation of methyl-, trichloromethyl- or trifluoromethyl substituted chloropyridines by cyclizing compounds having the formula ##STR1## wherein R is chloro and R" is methyl or trifluoromethyl, R is methyl, trichloromethyl or trifluoromethyl and R" is hydrogen or R and R" are both methyl.